Researchers use sensor devices to measure pH levels in the ocean. pH levels in the ocean are related to the amount of CO2 dissolved in the ocean. By measuring the pH levels in the ocean at various depths, researchers may be able to monitor Global Warming risks and ocean health. Some pH sensors are capable of measuring these levels by immersing ion sensitive field effect transistors (ISFETs) into the ocean. In the oceans, there is an inverse relationship between water temperature and pressure. Near the surface, temperatures are high and pressures are low. In deep sea, temperatures are lower but pressure is high. Such wide pressure variation can limit conventional pH sensor accuracy because of the measurement errors induced by large mechanical stresses associated in deep seas.